Capsules for the preparation of beverages, comprising a body of polymeric material obtained in a manner known per se, for example by means of an injection-moulding process, are known. A capsule of this type is described for example in European patent EP 1608569, in the name of the same applicant.
This known capsule comprises a casing with a slightly frustoconical form which may be manufactured, for example, by thermoforming a sheet of food-grade polypropylene or by means of injection-moulding. The casing has a continuous perimetral top edge projecting towards the outside of the capsule in the radial direction and a bottom perimetral edge. The capsule also comprises a bottom provided with at least one hole through which the beverage being prepared may pass.
The top perimetral edge and the bottom perimetral edge are sealed, respectively, with a top foil and a bottom foil, both made of aluminium, or other food grade material known per se. The expression “sealing an edge” is understood as meaning applying a foil to the top edge or bottom edge of the capsule so that there is no fluid communication between the inside and outside of the capsule through this foil. In a manner known per se, in fact, the edges sealed by means of the foils prevent the coffee powder from losing its organoleptic properties as a result of coming into contact with air.
The bottom divides the inside of the capsule into two zones: a first zone which contains the coffee powder, and a second zone inside which the beverage being prepared is temporarily collected.
This type of capsule envisages the use of a machine provided with means for perforating the top foil of the capsule, able to create a plurality of holes through which hot water is injected inside the top chamber at a very high pressure, for example of between 7 and 20 bar.
The second foil of the capsule is perforated by a punch so as to create a kind of spout, just before percolation of the beverage through the holes commences. Owing to the combined effect of the pressurised hot water supplied in the top chamber and the form of the bottom wall, the beverage fills the bottom chamber with a turbulent motion which favours frothing of the fatty substances.
The capsules of this type, although widely used, are not without drawbacks.
In fact, although the top foil is effective for preserving the organoleptic properties of the product contained inside the capsule, suitable perforation means are required in order to allow the water to pass inside the capsule.
Means for perforating the top foil of the capsule provided on the filter holder unit of professional coffee-making machines are known. These perforation means consist of perforating tips which perforate the top foil of the capsule when the filter-holder is fixed to the body of the machine.
Alternatively separate perforation means, of the hand-held type, are known, these allowing the capsule to be perforated before it is inserted inside the filter holder. The operation is not always easy and could give rise to incomplete perforation or tearing of the top foil.
Moreover, once the capsule has been used, separation of the top foil from the capsule body is not always easy since the foil tends to be break in the vicinity of the holes which have been previously formed.